The present invention relates to an oil detecting system for detecting oil leakage from equipments or parts constituting a plant or a vehicle, particularly, capable of computing or operating a leakage film thickness, leakage area and leakage quantity and specifying the type of leaking oil and oil leaking portion.
In a known art, there have been provided various methods for detecting oil leakage from equipments or units in a plant, including a method of visually observing oil leakage by workers, a method of locating a dish-shaped oil pan to a portion at which an oil leakage is expected to drop in the oil pan, a method of detecting oil leakage by utilizing a change in capacitance or resistance due to oil infiltration collected in an oil pit, and a method of detecting an oil leakage by detecting a change in transmissive light intensity by utilizing an optical fiber cable system.
Furthermore, an oil leakage from an engine of a vehicle under manufacturing is detected by a method of irradiating ultraviolet-rays on a leakage oil to thereby detect fluorescence of the oil. In this method, in order to external disturbance such as an influence of a fluorescent lamp, it is necessary to dispose the engine and the oil leakage detecting device in a dark room and to dispose a visual light cut filter in front of a black light (ultraviolet lamp) to prevent fluorescence wavelength of the oil to be detected from being overlapped at a time of irradiating the ultraviolet rays to thereby irradiate only the ultraviolet ray area. The fluorescence of the oil through the ultraviolet irradiation is amplified by an image intensifier and photographed by a CCD camera.
In the above various oil detecting methods in the known art, the visual method includes a problem such that the workers cannot be always visually inspect every position and inspecting ability of the workers differs from respective workers. It is also difficult for the workers to always continue the visual observation.
In the method of detecting oil leakage through accumulation of the oil in the oil pan or oil pit, it is difficult to detect the oil leakage in an early stage of the leakage and also difficult to determine the oil leaking portion and it is also necessary to ensure a position of the location of the oil pan or oil pit.
In the method of utilizing the optical fiber cables, it is necessary for the leaking oil to contact the fiber cables and, accordingly, it is difficult to exactly specify the oil leaking portion and oil leaking condition.
Still furthermore, in the oil leakage detection from the parts of a vehicle such as engine, it is necessary to specifically set a dark room or portion, providing a troublesome problem. Moreover, a fluorescent luminescence is caused to the engine parts, for example, formed of resin material, due to the irradiation of the ultraviolet rays, which may be erroneously detected as oil leakage, and since a fluorescence intensity is very weak, it is necessary to add a fluorescence agent to increase the fluorescence intensity for a certain oil. It is also difficult to discriminate the kind of the leaking oil.
Furthermore, the prior art for measuring an oil film thickness using the fluorescent method includes a method and an apparatus for measuring an oil quantity on the surface of a steel plate under production, for example, disclosed in Japanese Patent Laid-open Publication No. HEI 4-18763. A laser beam is applied to an oil-coated steel plate or the surface of the steel plate to make the oil fluoresce. Then, by measuring the fluorescent spectrum intensity of a component contained only in an oil in the fluorescence emitted from the surface of the steel plate, it is possible to obtain the thickness of a coated oil film because the fluorescence intensity is proportional to the film thickness. However, when actually performing oil film measurement, the measured value of a fluorescence intensity is influenced by the surface roughness of a substrate steel plate or a steel plate in coil. Therefore, an analytical curve showing the relation between fluorescence intensity and coated oil quantity for each surface roughness is previously prepared to obtain a coated oil quantity from the analytical curve and a fluorescence-intensity measurement result. When a coated area has been already known, it is possible to easily estimate a film thickness in accordance with the coated oil quantity.
The art for measuring an oil leaking area includes an oil-cell damage decision apparatus for citrus and the like disclosed, for example, in Japanese Patent Laid-open Publication No. HEI 6-129987. The apparatus and the citrus to be inspected are put in a dark room in order to prevent the influence of a disturbance due to a fluorescent lamp or the like and the surface of the citrus is irradiated with ultraviolet ray or light to make a damaged portion of oil cells fluoresce. Then, the fluorescent area of the damaged portion is obtained by selecting a spectrum region with a high intensity in the fluorescence by a filter, observing the region by a high-sensitivity camera or light detection sensor, and applying image processing or signal processing to the region.
Moreover, if a high-pressure hydraulic oil leaks due to a very-small damaged portion on a unit used for a plant, the oil spouts at a high pressure and, hence, the oil may scatter in a wide area in the form of fine particles. A visual inspection of units through a patrol of a worker, an oil sensor whose capacitances or resistances are changed due to oil contact, and an optical-fiber sensor whose refraction factors are changed are known technique for detecting the foggy leakage oil.
Furthermore, a method for detecting leakage of an oil in accordance with the difference of reflectance between water and oil by irradiating the water surface with a laser beam and detecting the reflected light is known as a technique for monitoring the oil leaking from a drain outlet of a plant or building.
However, in the prior art techniques mentioned above, when applying the oil film measuring apparatus disclosed in Japanese Patent Laid-open Publication No. HEI 4-18763 or the oil-cell decision apparatus disclosed in Japanese Patent Laid-open Publication No. HEI 6-129987 to the detection of oil leaking from a unit in a plant or a part of a vehicle or the like, the following problems occur.
Firstly, the apparatus cannot be used under a bright environment where disturbance light such as sunlight or illumination is present. This is because the number of disturbances increases and accordingly, the disturbance light ratio S/N to the fluorescence intensity of an oil to be detected is decreased.
Secondly, the film thickness measuring accuracy is lowered due to aged deterioration of an irradiation apparatus. The fluorescence intensity of the oil depends on the irradiation intensity of an irradiation apparatus in addition to a film thickness. Therefore, as the irradiation apparatus is deteriorated and the irradiation intensity is degraded, the intensity of the fluorescence emitted from an oil is weakened even if the film thickness is not changed. As a result, because an oil detector computes a film thickness in accordance with a fluorescence intensity, it decides the film thickness more thinly.
In addition to the above problems, the conventional oil detection technique using the fluorescence method cannot compute the film thickness distribution, area, or quantity of an oil leaking from a unit in a plant or a part of a vehicle or the like or specify the kind or type of the oil.
In the case of the visual inspection of units in a plant, it is not preferable that an inspector patrols in the atmosphere of foggy leakage oil from the viewpoint of safety. Under a state in which the field of view may be impaired like the above situation, it is difficult to specify a leakage portion.
Moreover, a capacitance- or resistance-type sensor has only a sensitivity for detecting the amount of oil leaking from a unit and dropped. It is difficult to detect foggy oil in which the oil becomes foggy fine particles and scatters in a wide area because the amount of oil to be detected by an oil sensor is very small.
An optical-fiber sensor decides a portion where oil adheres to a fiber as a leakage portion. In the case of the detection by the optical-fiber sensor, there is a problem that it is difficult to specify a leakage portion because foggy leakage oil scatters in a wide area and adheres to a fiber widely.
The reflection-type oil detection technique for detecting whether oil leaks from a drain outlet of a plant or building in accordance with the difference of reflectance between water and oil detects leakage oil by using the fact that the reflectance of thin-film oil floating on water surface is larger than that of water. Therefore, the reflection-type oil detection technique provides a problem that a substance with a reflectance larger than that of water may be detected other than oil. Moreover, the reflection-type oil detection technique also provides a problem that it is impossible to obtain the thickness, leakage area, quantity, and type of an leaking oil.